Loudspeaker drivers typically include the following components: an electromagnet, a moving voice coil, and a speaker cone attached to the coil. The speaker driver components operate together to generate audible sounds, such as music or voice transmissions. The electromagnet receives sound transmissions in the form of electrical signals from a sound amplifier, and the variations in the signal frequency and amplitude cause the magnetic flux of the magnet to change in response thereto. The vibrating voice coil and a sound conversion component, such as a speaker cone, are responsive to the changes in magnetic flux and move in a manner characteristic of the frequency and amplitude of the signal.
The speaker cone is the component that is responsible for converting the electrical signals into audible sound. The movement of the speaker cone displaces the air in the vicinity of the speaker cone. The displaced air creates sound waves having amplitudes and frequencies indicative of those from the electrical signal, and in this manner the desired audible sound reproduction is achieved.
The speaker drivers are typically enclosed in a sturdy, non-vibrational housing. The electromagnet and voice coil are recessed into the housing, and the face of the speaker cone is generally focused outward from the housing to direct the audible sound outward into the listening area. A perforated grill made of a rigid material, such as plastic or metal, or an acoustically transparent foam is placed over the exposed surface of the speaker cone for protection.
It is known in the audio reproduction arts that the transmission of vibrations to the body intensifies the enjoyment of listening to music. For example, in U.S. Pat. Nos. 4,064,376 and 4,354,067, which are herein incorporated by reference in their entirety, two devices for the implantation of a vibration device within a seat and backrest, respectively, of a chair are disclosed. The audio sensation created by the vibrations transmitted through the body cavity of the person sitting in the chair intensifies the enjoyment of the music. In U.S. Pat. No. 4,757,548, which is herein incorporated by reference in its entirety, a speaker that transmits sonic vibrations to liquid and solid media is disclosed. U.S. Pat. No. 4,778,027, which is herein incorporated by reference in its entirety, teaches the placement of speakers faced toward a surface to be vibrated. During operation, the sonic energy generated by the speaker is transmitted to the surface, causing the surface to vibrate.
It is also known in the audio reproduction arts to use sound induced vibrations to aid the hearing impaired. In U.S. Pat. Nos. 3,423,544 and 2,858,376 respectively, each of which is herein incorporated by reference in their entirety, two electro-acoustic bone conduction receivers mounted onto the elongated portion of eye glasses are disclosed. The bone conduction receiver as described in these references is an electromechanical device that transforms electric currents into mechanical vibrations and transmits the latter to the bones of the skull of the wearer of the glasses in the vicinity of the ear. This process of transmitting sounds to the inner ear of a deaf person is known to give good results in many instances where the inner ear is in reasonably good condition, although the middle ear may be seriously defective.
In U.S. Pat. Nos. 4,961,227 and 5,125,031, each of which is herein incorporated by reference in their entirety, loud speaker systems for transmitting vibrations are disclosed that include a speaker cone, a propagation member, and a housing that encloses the speaker cone and the propagation member. Generally, the vibrations on the speaker cone are transmitted to the housing through the propagation member. In some embodiments, the propagation member can extend through the housing or can include a vacuum environment within the housing.
In some settings, it is desirable that the vibrations from a loudspeaker be directly felt by a human body in more accurate and focused fashion. For example, the human body's feeling of the vibrations generated by music can be used to convey rhythm, timing, and steps to the deaf. In another example, when a person listens to music, the body feeling towards vibrations of the loud speaker enables the person to sense how hard and how quick the player strikes the keys of a piano. In some other settings, in addition to the requirements of more accurate and focused vibration transmission, it is also desirable to transmit the vibrations from the loudspeaker to the human body without transmitting audible sounds from the loud speaker. For example, loud speakers can be installed in a chair so a person sitting in the chair can feel the vibrations without disturbing others.